In medical specimen testing, purified water may be dispensed for various purposes. In certain clinical analyzer instruments used to test for the presence of an analyte in a bio-fluid sample (otherwise referred to as “specimens”), it may be desirable to precisely meter water to be used in the process. For example, in some automated testing systems (e.g., clinical analyzer instruments), specimens contained in sample containers (such as test tubes, sample cups, vials, cuvettes, and the like) may be tested to determine a presence of a particular analyte or substance contained therein. As part of this process, precise metering of a process fluid (e.g., purified water) may be desired. In order to provide for testing accuracy, such metering should be relatively precise.
For example, in some testing methods, such as the so-called “chase method,” a volume of sample fluid is first aspirated and dispensed by a metering apparatus, and the dispensing of this sample fluid is followed (chased) by dispensing a precisely-metered volume of a process fluid (e.g., purified water). In the chase method, the volume of dispensed process fluid may be greater than the volume of the sample fluid that is dispensed. In the so-called “neat method,” a small amount of sample fluid is aspirated and dispensed (on the order of 1-3 μL). In the neat method, the process fluid itself (e.g., purified water) may be the vehicle that allows for the metering of the sample fluid, even though the process fluid is not itself dispensed in the neat method. However, for both methods, it should be understood that inaccurate metering may lead to errors in specimen testing.
Accordingly, methods, systems, and apparatus that may improve accuracy of metering of a process fluid (e.g., purified water) are desired.